Capacitance Sensors

Technology Explainer

Capacitance sensors measure soil moisture based on the dielectric permittivity of the soil. They use an oscillating electric field to detect changes in soil capacitance, which correlates with soil moisture content.

Accuracy

The problem is that most capacitance sensors have a too low dielectric measurement frequency of <100 MHz. This severely impacts accuracy and leads to an error range that is +- 6% of absolute measurements of VWC, at best.

In the case of probes that are pushed into the ground, preferential water flow along the probe leads to further reduction in accuracy.

Price

Capacitance sensors are usually quite cheap and are therefore affordable to most operations.

Installation & Maintenance

Depending on the type of sensor, probe or buried sensor the installation process can vary. However, overall the process is fairly straightforward.

Soil Types

Capacitance sensors can work in all soil types. However, for most sensors it is necessary to calculate each sensor individually to the soil type. Furthermore, heterogeneous soils are a challenge as the sensor surface of many capacitance probe sensors is very small.

Measurements

Summary

Cost-Effective: These sensors are relatively inexpensive, making them accessible to a broader range of farmers.

Ease of Use: Capacitance sensors are generally easy to install and use, requiring minimal technical knowledge.

Real-Time Monitoring: They provide continuous real-time data, which is beneficial for precise irrigation management.

Sensitivity to Soil Types: These sensors can be sensitive to variations in soil types and require calibration for different soil conditions.

Lower Accuracy: Compared to TDT sensors, capacitance sensors might be less accurate, particularly in heterogeneous soils.

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